Objective: Previous epidemiological studies
on relationships between mental health status and
sleep status of adolescents have not been sufficiently
representative. In the present study, using
samples representative of Japanese adolescents
nationwide, associations between mental health
status and various sleep statuses were examined.

Method: The survey was conducted in December
2004 and January 2005 among students enrolled
in randomly selected junior and senior high
schools throughout Japan, using self-administered
questionnaires that addressed lifestyle, sleep status,
mental health status, and personal data. Of
103,650 questionnaires collected, 99,668 were
analyzed. Sleep status was assessed according to
sleep duration, subjective sleep assessment, bedtime,
and insomnia symptoms. The Japanese version
of the 12-item General Health Questionnaire
was employed for assessment of mental health
status.

Results: Mental health status of subjects
whose sleep duration was less than 7 hours, and
those who slept 9 hours or more, was poorer than
that of subjects who slept for 7 hours or more but
less than 9 hours. A U-shaped association was
observed between mental health status and sleep
duration. Furthermore, a linear association was
observed between subjective sleep assessment
and mental health status; the worse the subjective
sleep assessment, the poorer the mental health
status. Mental health status was also inversely
proportional to the frequency of insomnia
symptoms.

Conclusion: The fact that sleep duration
and subjective sleep assessment showed different
patterns of association with mental health status
indicates that these 2 sleep parameters have independent
significance. Considering these associations,
it is important to promote mental health
care and sleep hygiene education for
adolescents.​